The present invention relates to a latching apparatus for an inflatable belt device which achieves reduction of gas leakage without losing the smoothness of insertion of the tongue into the buckle, or reduction in the manufacturing cost and the weight of the latching apparatus. More particularly, the present invention relates to a latching apparatus for an inflatable belt device comprising a tongue and a buckle through which gas generated from an inflator is supplied to a cushion.,
Currently, a seat belt is the most commonly used as a device for restraining an occupant in a vehicle seat in the event of emergency. A typical seat belt device comprises a shoulder webbing to be extended diagonally across the chest from the shoulder to the waist of an occupant, a lap webbing to be extended across the lap in front of the waist of the occupant, the shoulder webbing and the lap webbing being integral as one strip. The proximal end of the shoulder webbing is connected to a seat belt retractor. The retractor prevents the shoulder belt from being withdrawn when an abnormal deceleration is exerted on a vehicle. When locked, the shoulder belt blocks the frontward movement of the occupant.
In recent years, seat belt devices have been refined to further intensify the function of protecting occupants by adding the following techniques:
(1) a pretensioner which rapidly remove slack from the webbing in the event of emergency to achieve initial restraint of the occupant; and
(2) an energy absorbing mechanism (hereinafter, referred to as xe2x80x9cEA mechanismxe2x80x9d) which allows the webbing to be gradually withdrawn to absorb inertia energy of the occupant when the tension on the webbing exceeds a predetermined value.
However, there remains a need for achieving more soft protection of the occupant by reducing the pressures to the shoulder and the chest of the occupant.
In order to meet this need an inflatable belt device has been developed. The conventional inflatable belt device is a seat belt, of which a portion of a shoulder webbing that touches the shoulder and chest of an occupant""s body is composed of an inflatable bag. For example, the bag may be inflated to have a diameter of 14 cm in order to function as an air cushion, thereby softening the pressure exerted on the occupant""s body. The bag is shortened in the longitudinal direction when inflated in order to remove the slack from the webbing. In this manner, the inflatable belt also functions as a seat belt pretensioner. Furthermore, the inflatable belt device can also function as an EA mechanism by gradually exhausting gas in the bag at appropriate times. It is expected that inflatable belt devices will increase in popularity due to their improved safety capacity as compared to current seat belt devices.
In general, an inflatable belt device may include a latching apparatus for connecting a seat belt device and a vehicle body. The latching apparatus generally comprises a buckle connected to a vehicle body (e.g. seat frame) and a tongue connected to an end of the inflatable belt. The buckle has a tongue latching mechanism for allowing detachable latching of the tongue.
Inflators for inflating a bag of an inflatable belt device generally include two types. One type is connected to an upper portion of the bag (arranged above the shoulder of the occupant) and the other type is connected to an lower portion of the bag (arranged below the lap of the occupant). In some of the second type of inflators, gas generated by the inflator is supplied into the bag through a buckle. The buckle and a tongue have gas passages, respectively, through which gas generated by the inflator is passed. These passages are designed to communicate with each other when the tongue is inserted to the buckle.
The inflatable belt mentioned above may be improved in several ways. In order to improve the smoothness of insertion of tongue into the buckle, a suitable clearance should be formed between the tongue and a tongue insertion opening of the buckle in the normal used state of a seat belt. In order to minimize gas leakage, gas generated by the inflator should be supplied into the bag through the passages of the buckle and the tongue without gas leakage when the inflatable belt is deployed (in the event of vehicle collision). Furthermore, easy detachment of the tongue from the buckle should be allowed after the vehicle collision.
An inflatable belt device that satisfies the above points may include a buckle having a gas passage of which one end is positioned inside the buckle so as not to project in the normal used state. The gas passage is arranged to project into the tongue only at the start of vehicle collision and to return to the inside of the buckle by pressure inside the bag during a period between the vehicle collision and the end of the vehicle collision.
In order to cope with a vehicle collision of relatively long period of time (for example, a roll-over that needs to restrain an occupant for several seconds of time), it is required to increase the capacity (molecular amounts of gas) of the inflator to maintain the pressure in the bag. However, the size and the weight of the inflator are increased with increase in the capacity of the inflator, thus also increasing the manufacturing cost. The inflator should be designed to have enough capacity to account for any gas leakage between the buckle and the tongue.
The present invention has been made to solve the aforementioned problems by providing a latching apparatus for an inflatable belt device which achieves reduction in the gas leakage without losing the smoothness of insertion of a tongue into a buckle, and which achieves reduction in the manufacturing cost and the weight of the latching apparatus.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.